1. Field of the Invention
The present invention generally relates to moisture resistant and water proof paper products utilizing a mixture of recycled paper and recycled paper containing hydrogenated triglycerides. Particularly, this invention relates to moisture resistant paper tray thermo-molded from a mixture of recycled paper pulp and recycled paper originally coated and/or impregnated with hydrogenated triglycerides primarily for use in the protein industry which encompasses poultry, meat and seafood. The tray can be repulped and recycled after use to be part of the feedstock for new paper products.
2. Description of the Related Art
Due to widespread environmental concerns, there has been significant pressure on companies to discontinue the use of polystyrene products in favor of more environmentally safe materials. Some groups have favored the use of products such as paper or other products made from wood pulp. However, there are drawbacks to the sole use of paper due to the tremendous amount of energy that is required to produce it and limited applications of same. Thus, there remains a need to find new, easily degradable materials that meet necessary performance standards.
Degradability is a relative term. Some products which appear to be degraded merely break apart into very small pieces. These small pieces are hard to see, but can still take decades or centuries to actually break down. Other products are made from materials which undergo a more rapid breakdown than non-biodegradable products. The adoption of products made of compostable materials which also meet a variety of needs, such as containers for fluid containing products which rest in a damp or wet condition, has posed a significant challenge.
Corrugated board is a converted or remanufactured paper product. It is a layered structure that is usually die cut to form corrugated containers. It consists of a fluted corrugated medium sandwiched between sheets of linerboard. The simplest three-ply corrugated board structure is known as “double face.” As recently as 1990, much of the linerboard was made entirely from virgin, long-fibred, softwood and kraft pulp. Today, however, these board grades contain sizeable percentage of recycled old corrugated containers (OCC) and many linerboards are made from 100% OCC.
OCC has a history of efficient recycling use. Today, most of this recycled material goes directly from retail chain stores to mills based on long-term contracts. The rest comes from municipal curbside collection and wastepaper dealers. Most OCC is used again to produce corrugating medium and linerboard in the production of boxboard with a lesser percentage of OCC used in packaging foodstuffs such as egg cartons and fruit separation.
Another source of pulp are the clippings which come from trimming and cutouts of cardboard boxes. These clippings are known as DLK which stands for double liner kraft.
“Repulping” refers to any mechanical action that disperses dry or compacted pulp fibers into a water slush, slurry or suspension. The action can be just sufficient to enable the slurry to be pumped, or it can be adequate to separate and disperse all the fibers. In a typical recycling process, bales of OCC are fed into a repulper where the material is disintegrated and the gross contaminants are removed. The resulting stock is pumped through pressure screens and cyclonic cleaners to remove oversized materials and foreign matter. The glue, staples, wax, and tapes originally used to assemble the corrugated box are also removed.
In the manufacture of paper and paperboard and of products made from same, petroleum derived paraffin waxes and synthetic polymers have been used for many years as moisture retardants, water repellents, oil repellents, stiffeners, strengtheners, and release agents. Paper and paperboard coated or impregnated with petroleum waxes resist biodegradation and composting when disposed of in landfills and other waste disposal systems. Besides paraffin, the material used most often in such paperboard products is polyethylene. However, other widely used polymers in the field include polymerized acrylics, vinyls, styrenes, ethylenes and copolymers or hetero-polymers of these monomers.
The paper and paperboard to which most coating materials are applied is difficult to repulp and recycle in standard paper mill processes because the petroleum derived polymers and, particularly, the petroleum waxes are non-biodegradable in mill white waters (circulated process waters) and discharge effluents. Furthermore, the residue of the petroleum waxes that is not removed from pulp fibers during the repulping and recycling processes causes severe problems due to buildup that occurs on the screens and felts used during the process of forming and making the paper or paperboard sheet. Paper and paperboard coated or impregnated with traditional synthetic polymers and hetero-polymers are also difficult or impossible to repulp and recycle owing to their resistance to separation from the fiber in the standard repulping processes resulting in significant fiber losses in efforts to repulp and recycle them. These products are also non-biodegradable and therefore resist composting.
Water repellent packaging currently utilizes petroleum based liquid polymers or polymer film laminates (including polyethylene or similar film laminates such as polyolefin, polyester, polyvinyl alcohol, polyvinyl acetate, polystyrene, polypropylene, and the like) which are recyclable after extensive treatment. All of the laminates require the installation of specialized repulping machinery that separates the pulp fibers from the laminated films and is far more expensive in terms of operating costs and/or recycled pulp fiber yields. Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops or waste paper. The action of separating the fiber from the film damages some fibers causing the damaged fiber to be separated out of the recycled pulp and presented for reuse. The separated film waste carries some of the fibers out of the repulpate when its adherence is not interrupted by the repulping process. Likewise, coatings and impregnating products made from or based on paraffin waxes and/or similar petroleum derivatives can be repulped for recycling in specially configured repulping equipment that removes and separates the paraffin waxes; however, as in the laminated film repulping process, the more intense physical and chemical requirements of this repulping process coupled with the lost fibers that become trapped in paraffin wax wastes cause the recyclable repulped fiber levels to fall far below those of standard repulping processes. Moreover, boxes and containers made from paraffin waxes are not biodegradable and must be separated and deposited in separate landfill areas.
Recently hydrogenated triglycerides have been impregnated and coated on paper and paperboard to give the paper and paperboard similar qualities to paraffin waxes. Another desirable quality of hydrogenated triglyceride coated and/or impregnated paper, paperboard and corrugated material is that the same is repulpable and biodegradable. These hydrogenated triglyceride paper products have become more widespread in the last 15 years and now comprise a small but growing segment of the marketplace.
The use of hydrogenated triglycerides to treat paper and paperboard is known in the prior art. In one example, U.S. Pat. No. 2,840,138 issued Jun. 24, 1958 discloses the use of tallow fatty acids to impregnate and penetrate corrugated paper material to provide a wilt resistant material. Also, U.S. Pat. No. 4,752,637 issued Jun. 21, 1988 is directed to a method of treating fiberboard to have superior moisture resistance with various mixtures of hydroxy terminated esters such as tallow.
U.S. Pat. No. 6,103,308 issued Aug. 15, 2000 is directed toward a paper and paperboard coating composition using vegetable oil triglyceride as a paper coating while U.S. Pat. No. 6,201,053 issued Mar. 13, 2001 is directed toward various triglycerides mixed with catalysts for use as a waterproofing agent on paper coating.
U.S. Pat. No. 6,846,573 issued Jan. 25, 2005 discloses the use of hydrogenated triglycerides having a melting point above 50° as a coating material for the surface of paper products to improve wet strength and moisture resistance in addition to being repulpable.
U.S. Pat. No. 8,455,068 issued Jun. 4, 2013 and U.S. Pat. No. 8,551,585 issued Oct. 8, 2013 disclose production of a moisture resistant poultry box using a cardboard impregnated with hydrogenated triglycerides and backing boards coated with polyethylene terephthalate (PET).
The use of plastic and Styrofoam® containers and trays for packaging and distributing food are widespread in the marketplace as are trays and containers made from polystyrene and polypropylene. However, trays and containers made from plastic and Styrofoam® are less eco-friendly than ones made from more biodegradable materials such as paper and cardboard. Molded paper pulp trays are degradable; however traditional molded trays from recycled old corrugated containers provide less structural rigidity than those of Styrofoam® and plastic. The need for improved structural stability is particularly pronounced with respect to single compartment trays made from paper pulp material particularly when the same is used in moist conditions. There is currently a need for molded pulp containers which are biodegradable, are easy to open and close but at the same time have the necessary strength and resist leaks. This is particularly true for fresh poultry, seafood and beef containers as these food products release fluid when sitting in the container and the containers are prone to leakage. This leakage can present health problems as well as present a poor sales appearance when placed in a store for sales. The moisture and leak resistance must also be maintained where the container is tilted or stacked at an angle, causing the liquid (blood, water, body fat) contained therein to be spilled.
Styrofoam® containers are widely used in the food industry. For example, fast food restaurants use molded Styrofoam® trays and drink containers. Manufacturers use Styrofoam® for product packaging in the forms of rigid end caps, corner guards, trays, bracing and blocking to provide structural integrity and protect goods from damage during transport. Distributors use Styrofoam® bulk food trays and containers. Currently, Styrofoam® trays are used to package and sell poultry, meats such as beef and pork and seafood products. Gardeners use Styrofoam® as a container for plants. However, the problem with Styrofoam® products is that they are not biodegradable and reusable, do not compost and occupy large areas in waste disposal.
Containers having a tray formed of molded paper pulp are often seen as an environmentally friendly option. However, the physical properties of the paper and corrugated board pulp material and the production processes of converting the pulp material into usable containers make it difficult to produce a pulp container or tray having sufficient strength to prevent tearing or puncture with leak resistant properties.
Molded pulp trays and containers provide the added benefit of using recycled material without the drawbacks of non-sustainable materials. Molded pulp products which are thermoformed are created entirely from recycled paper, making it one of the most sustainable and environmentally friendly solutions. This is beneficial because paper accounts for approximately at least 40% of municipal waste. In fact, the United States alone uses more than 100 million tons of paper each year. The paper industry is the third largest consumer of energy in the United States, and is one of the largest water polluters in the world.
Recycled paper ameliorates many of these deleterious impacts. For example, recycled paper uses 60-70% less energy to produce than virgin pulp. Recycled paper uses 55% less water, reduces water pollution by 35%, reduces air pollution by 74% and eliminates many toxic pollutants. Furthermore, recycled pulp helps preserve forests by reducing the need for loggers to cut new timber.
Molded paper pulp products are porous and quickly absorb moisture. Saturated with moisture, molded paper pulp loses its rigidity and begins to deteriorate.
Currently, molded paper pulp products are among the fastest biodegradable products known. Generally they take only two to five months to fully biodegrade under normal conditions.
It is, therefore, desirable to provide a recyclable tray product and a method for making same that combines the biodegradability of molded pulp container with the utility of a Styrofoam® container to replace Styrofoam® container currently in use.